Maybe When You're Older

If you turned in the previous quest Ptrust Fall, but did not click the Pterrordax to get the flight back, you won't get credit for the return.
How to go back:
Take a Goblin Glider Kit.
Start at Pa'ku's Nest, look on your right, jump down and use the glider to reach the [npc=135594] (north-west of the lake on your world map). You'll see a yellow dot on your minimap when you are near.
Fly circles until it is save to land. Click [npc=135594].
Turn in the quest.

/way 70.9 51 Start at nest
/way 72.45 57.20 Child of Pa'ku

After this comes Eyes on the Skies.

If like me you were also on the other buging quest with Pa'ku (the quest that can't be validate), it will makes this quest bug.
When you gonna reach the nest you gonna see your character jump on another pteranodon and change direction to Dazar'alor, and that isn't normal.
Delete that buging quest and go back on the bottom, Pa'ku will still be her.
The only way to validate that quest is to reach the nest with the kid of Pa'ku, as intended. If you try to go without that to the nest, it won't validate it.

I hope my comment will help people in the same situation than me.